1. Field of the Invention
The present invention relates generally to means for packaging microelectronic devices. More particularly, the invention relates to improved, SIMM and DIMM type memory modules.
2. Description of Related Art
Multichip module (MCM) assembly is currently an enabling technology for improving system performance in high-end workstation and super computers. By interconnecting multiple bare dice on a single substrate, packaging density is increased and chip-to-chip communication distance is consequently shortened, enabling higher operating speeds. Small, lightweight consumer products such as notebook or handheld computers and telephony products are expected to benefit from the improved miniaturization that MCM technology accomplishes. Unfortunately, this technology is currently too expensive for most of these applications.
A principal reason for the expense associated with multichip modules is that the technology is constrained to low volume, custom applications which cannot attain sufficient market volumes to help drive manufacturing costs down. Part of this problem is exacerbated by a current shortage of reliable, high-volume sources for the large variety of “known good die” required by many MCM applications. “Known good die” are semiconductor IC chips that are fully tested and screened to the same level of reliability as individually packaged parts, and are a fundamental necessity for attaining high MCM assembly yields with minimum repair. There has been recent progress in solving some of the handling issues with respect to bare die testing for both single die and dice still in wafer form, so this problem appears to be resolvable. However, identifying and implementing a high-volume, industry standard MCM application is still proving elusive.
One potential mass market is represented by industry standard Single Inline Memory Modules (SIMM) and Dual Inline Memory Modules (DIMM). These products have annual volumes reaching millions of units. Memory modules typically consist of identical IC device types, eliminating the need for stocking a large variety of “known good die”. Memory modules, however, are noted for being a highly competitive, low-margin product. Because memory modules are assembled on small area, printed circuit boards, using highly automated processes, they have low associated material and assembly costs. Hence, the standard memory module business is widely thought to be too cost-driven to be considered a good candidate for MCM technology. However, high-end computing platforms, such as blade servers, tower servers and graphic accelerator cards are anticipated to require higher performance memory modules operating above 800 MHz which would benefit from improved module designs.
Some patents relating to memory modules include the following: U.S. Pat. No. 4,656,605, “Single In-Line Memory Module;” U.S. Pat. No. 4,727,513, “Single In-Line Memory Module;” and U.S. Pat. No. 4,850,892, “Connecting Apparatus for Electrically Connecting Memory Modules to a Printed Circuit Board.” Additional patents in this area include U.S. Pat. No. 5,661,339; U.S. Pat. No. 5,708,297; U.S. Pat. No. 5,731,633; U.S. Pat. No. 5,751,553; U.S. Pat. No. 6,049,975; U.S. Pat. No. 6,091,145; U.S. Pat. No. 6,232,659; U.S. Pat. No. 6,665,190; and Japanese Patent 3424929. None of the foregoing discloses means for cooling the interior of the modules.